Optical chemical sensors have been developed for monitoring the concentration of a variety of chemical constituents, including molecular O2, pH and carbon dioxide. These sensors have significant advantages over the more traditional electrochemical sensors, such as electrical isolation from the environment measured, small size, immunity to calibration drift arising from sensing membrane fouling, and compatibility with non-contacting measurements. Applications include, for example, monitoring conditions within fermentation and cell culture bioreactors, and ultra-pure water, such as is used in the fabrication of semiconductors.
Although such conventional optical chemical sensors are extremely effective in monitoring various concentrations in a variety of situations, various deficiencies are encountered with the use thereof. For example, conventional optical chemical sensors experience photobleaching over time, thereby requiring the frequent replacement or service of the sensors. However, in conventional systems, the replacement or service of optical chemical sensors is a laborious, time consuming effort.
Furthermore, when repairing or replacing conventional optical chemical sensors, a portion of, or even the entire system/process, must be shut down to enable replacement or service of the sensors. Moreover, depending on the nature of the system under investigation, replacement or service of the sensor may be impossible, and failure of the sensor may lead to a complete overhaul of the system, such as emptying the system of all components, cleaning the entire system thoroughly, and restarting the system from scratch.
In view of the disadvantages associated with the use of conventional optical chemical sensors in environments such as fermentation and cell culture bioreactors, it is an object of the present invention to provide an optical chemical sensor feedback control system which can determine the proportional luminescent emission response of sensors (such as sensing films).
It is a further object of the invention to provide an optical chemical sensor feedback control system which is capable of monitoring the status (i.e., the luminescent emission response) of the luminescent sensing film, and adjust the magnitude of the photoexcitation thereof accordingly, so as to obtain satisfactory luminescent emission data.
It is a further object of the present invention to provide an optical chemical sensor feedback control system which, when the system determines that the luminescent sensing film is exhibiting an unsatisfactory response, can adjust and/or replace the optical chemical sensors as needed, while eliminating and/or minimizing disturbance to the environment monitored.
It is another object of the present invention to provide a method of feedback control of an optical chemical sensor, wherein the optical sensor, comprising a luminescent sensing film, is utilized, monitored, and replaced/adjusted as needed, and the magnitude of the photoexcitation thereof is adjusted based on calibration data and historical luminescent emission response data.